Valve actuator differential worm planetary gear drive

ABSTRACT

A valve actuator differential worm planetary gear drive provides forward or reverse motion to a valve stem, from an input from either a motor-driven worm or a handwheel drive worm, by using a plurality of planet gears to send motion to the sun gear. If the preference is to have the motor drive the valve primarily, the manual worm stays locked and the motor worm acts as a planetary arm. When it is desired to move the valve by hand, the motor gear is fixed and rotation of the handwheel worm gear transmits the power through the ring gear and the planet gears to the drive sleeve.

CROSS-REFERENCE TO RELATED U.S. APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 07/173,195, filed Mar. 24, 1988, now U.S. Pat. No. 4,896,562,issued Jan. 30, 1990, for VALVE ACTUATOR DIFFERENTIAL WORM PLANETARYGEAR DRIVE.

BACKGROUND OF THE INVENTION

General valve application requirements dictate that motorized valveactuators or operators must have provision for manual operation in caseof power failure or in the case of initial installation and set-up whenpower may not be available. Safety requirements dictate that the powerand manual drives operate independently so as to preclude movement ofthe manual input (handwheel, lever, etc.) during power operation.Traditionally, the requirement for independent manual operation has beensatisfied by placing a clutching device within or attached to theactuator power train. The function of the clutching device is to natedrive (manual or power).

Engagement or disengagement of the clutching device can be accomplishedby several means including: (i) depressing a lever to move a clutchelement; (ii) pushing or pulling a handwheel into engagement; and (iii)rotating a handwheel which causes clutch elements to engage.

All of the above provide for totally independent drive, either manual ormotor, i.e., the drive arrangement is either motor or manual, the drivesare never engaged simultaneously.

Other types of clutches may be used which provide for single directionpower transmission, i.e., clockwise or counterclockwise torque may betransmitted via a handwheel through the clutch to the power train butmay not be transmitted from the power train through the clutch to thehandwheel. Clutch arrangements of this type have the inherentdisadvantage of back-driving the power element unless the power elementis disengaged by alternate means.

Also known in the art is the valve actuator disclosed in U.S. Pat. No.4,261,224 to Sulzer. There, a valve actuator is operable alternativelyby a motor or manually. The motor is coupled through a special one-waycoupling to the sun-gear drive of the planetary assembly which permitsthe motor to drive the sun gear in either direction upon rotation of themotor but prevents rotation of the sun gear when the motor is arrested.A handwheel is coupled to the ring-gear drive of the planetary assemblythrough a worm and pinion so that the handwheel may then drive the ringgear under manual operation, but the ring gear is retained againstrotation by the worm pinion when the handwheel is idle.

SUMMARY OF THE INVENTION

A valve actuator mechanism that may be operated by either amotor-provided input force or a hand-operated input force is disclosed.The motor-provided force is transmitted through a worm and gearcombination to the sun gear, which, in turn transmits the force toplanet gears adjacent thereto. The planet gears transmit the forcethrough planet carrier arms to the drive sleeve and that component movesthe valve stem in the correspondingly proper direction. If control ofthe stem is to be provided by the handwheel, the worm and gearcombination attached thereto transmits the input force to the ring gear,which transmits it through the planet gears, to the drive sleeve andstem, as described above. Either the motor worm and gear or thehandwheel worm and gear will self-lock by setting the geometry of thehandwheel and automatic worm gear sets so that the tangent of the helixangle of the gear is less than the coefficient of friction, therebypreventing back-driving, when the alternate has power applied thereto.

In an alternate embodiment, planet gears are attached to a motor-drivenworm gear, and the ring gear is attached to and rotates with, thehandwheel driven worm gear. Motor input causes the worm gear to drivethe sun gear whereas with handwheel operation, the planet gears areidler gears and force from the handwheel worm gear is transmittedthrough the ring gear, the idle planet gears and to the sun gear. Inboth cases, the sun gear drives the actuator sleeve and hence, the stem,which moves the valve.

It is therefore an object of the present invention to provide a valveactuator mechanism that allows either motor-driven or hand-operatedinput while, through design of helix angle of both the worm teeth andgear teeth, operation of one causes automatic self-locking of the other.

It is a further object of the present invention to provide a valveactuation mechanism which does not use a clutching device to disengagethe unused input device during operation.

It is a still further object of the present invention to provide a valveactuation mechanism that provides forward or reverse motion to a valvestem, from an input from either a motor-driven worm or a hand-operatedworm, by using planet gears to send motion to the sun gear. These andother objects and advantages of the present invention will be readilyapparent to those skilled in the art by reading the followingDescription of the Preferred Embodiment and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational view of a valve actuator mechanism 10 withcasing 11 cut away and the valve stem and drive sleeve partially cutaway to show the motor worm;

FIG. 2 is a sectional view of valve actuator 10 taken along lines II--IIof FIG. 1;

FIG. 3 is a sectional view of valve actuator 10 taken along linesIII--III of FIG. 2;

FIG. 4 is a sectional view of valve actuator 10 taken along lines IV--IVof FIG. 2;

FIG. 4a is an exploded, schematic illustration of the geometricrelationship between the helix angles of the worm teeth and the gearteeth of FIG. 4;

FIGS. 5a and 5b are schematic representations of valve actuator 10 witharrows showing how control and power are transferred from the motor(FIG. 5a) or the handwheel (FIG. 5B).

FIG. 6 shows a sectional view, similar to FIG. 2, of an alternateembodiment of valve actuator 10' with the sun gear 50' connecteddirectly to the actuator sleeve 60' and the planet gears 40' connectedto the motor worm gear 35'; and

FIGS. 7a and 7b are schematic representations of valve actuator 10' witharrows showing how control and power are transferred from the motor(FIG. 7a) or the handwheel (FIG. 7b).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows an elevational view of the actuator mechanism 10. Mechanism10 is housed in a casing 11, as for example bottom casing 11a with topcasing 11b bolted thereto as is known in the art, and FIG. 1 showscasing 11 cut away for sake of clarity. Mechanism 10 can be made fromstainless steel, or other similar material, and controls the movement(as will be described of a stem 59 in a drive sleeve 60, said stem 59being operatively connected to a valve (not shown).

As seen in FIG. 1, valve actuator 10 has both a motor driven input 18from motor 14 and a hand-operated input 15 from a handwheel 16. (Note:the stem 59 and drive sleeve 60 have been partially obscured in FIG. 1to show the motor worm 25.) Motor shaft 18 is connected to a gear 19,which gear 19 intermeshes with, and turns, a gear 22, as is known. Gear22 is connected to a shaft 23 containing motor worm 25.

The input 15 from handwheel 16 can be seen at the top end of actuator 10in FIG. 1. Shaft 15 is coupled to a worm 26 (shown in phantom in FIG. 1)which, in turn, is coupled to handwheel worm gear 28. Drive sleeve 60 issecured in actuator 10 is by clamping mechanisms 31a, b, as is known,with shims 32a, b to provide proper fitting thereto. With power fromeither motor input 18 or handwheel input 15, planet gears 40 and ringgear 80 allow transfer thereof (as will be explained) to drive stem 59,to enable drive stem 59 to move a valve (not shown) to an open or closedposition. As is known in the industry, both motor worm gear andhandwheel worm gear contain self-locking characteristics that preventany motion thereof when that drive input is not being utilized.

FIG. 2 shows a sectional view of valve actuator 10 taken along linesII--II of FIG. 1, and shows the working relationship between motor worm25 and motor worm gear 35 (shown in phantom in FIG. 1) and the workingrelationship between handwheel worm 26 (shown in phantom in FIG. 1) andhandwheel worm gear 28. The power-transferring relationship between worm25 and gear 35 can be seen also in FIG. 4, which is a sectional viewtaken along lines IV--IV of FIG. 2. Gear 35 is free to rotate arounddrive sleeve 60 at the interior thereof, and rests and moves againstspacer 30 as is shown. As seen in FIG. 4, gear 35 carries a plurality ofkeys 37 (shown in phantom in FIG. 2) that lock into keyways 38 in sungear 50, thereby forcing rotational movement of gear 50 whenever inputmotion is transmitted by worm 25 to gear 35. With reference to FIG. 4a,an exploded, schematic illustration of the geometric relationshipbetween the helix angles of the worm teeth and the worm gear of FIG. 4,the self-locking characteristics of the instant invention will beexplained. The helix angle 0 of the worm and the worm gear is designedto be no greater than 5 degrees for an environment of, for instance, asmooth steel worm operating on a bronze worm gear in well-lubricatedgear set. The helix angle is designed as such with the tangent of 0 lessthan the coefficient of friction, so that the gear set, either motorworm 25 and gear 35 or handwheel worm 26 and gear 28, does not backdrive (i.e. worm drives gear but gear cannot drive worm).

Immediately adjacent a ledge 52 of sun gear 50, is a support washer 53to provide moving support to planet gears 40. As shown in FIG. 3, asectional view taken along lines III--III of FIG. 2, planet gears 40 areoperatively coupled between the teeth of ring gear 80 and the teeth ofsun gear 50. Each planet gear 40 is identical to the others and so thedescription herein provided pertains to all. Gear 40 is in the generalform of a right cylinder with teeth distributed around the outsidethereof as is known. A shaft 41 runs throughout the center of gear 40and is affixed, as by pin 42a to one of a plurality of carrier arms 47.A second pin, or the like, 42b is used to secure bottom section 43thereto, which section 43 slides over support washer 53, as describedabove. Carrier arms 47 are fixed to drive sleeve 60, as by keys 48(shown in phantom in FIG. 2) and have needle bearing 49 adjacent the topthereof.

Ring gear 80 surrounds the planet gears 40 (see FIG. 3) and is coaxialwith stem 59. Ring gear 80 rests on needle bearing 49, and is affixed tohandwheel worm gear 28, as by keys 58 (shown in phantom in FIG. 2) as isknown.

FIGS. 5a and 5b show a schematic representation of valve actuator 10with arrows showing how control and power is transferred from either themotor-driven worm to the stem (FIG. 5a) or the handwheel worm to thestem (FIG. 5b). FIG. 5a shows that the motor provided force istransmitted through a worm 25 to worm gear 35. The motion is transferredfrom there through sun gear 50 to planet gears 40. Since the handwheelworm gear prevents motion of ring gear 80, the moving planet gears 40force carrier arms 47, and drive sleeve 60, to transfer movement todrive stem 59. FIG. 5b shows that when motion is transferred throughworm 26 and gear 28 to ring gear 80, the reaction of gear 80 on planetgears 40 transfers the force through carrier arms 47 to drive sleeve 60and stem 59. If a different reduction preference (of the gears) isdesired, the handwheel worm connection and the motor worm connection maybe reversed.

FIG. 6 shows a sectional view (similar to FIG. 2) taken along thevertical axis of an alternate embodiment of the valve actuator. (In FIG.6, the worm 25' coupled to the motor is shown on the opposite side ofmechanism 10' than shown in FIG. 2.) Mechanism 10' has stem 59' coaxialwith sleeve 60', which sleeve 60' is connected to sun gear 50', asshown. Bushings 39a, b, respectively, further enclose drive sleeve 60'to allow free rotation therearound by handwheel worm gear 28' and motorworm gear 35'. Surrounding bushing 39b is worm gear 35' which is on topof bushing 31a, is circular in shape, and has a plurality of gear pins41' spaced evenly apart and bolted therethrough. Rotating freely on eachof pin 41' is a planet gear 40'. Fixed to the central part of drivesleeve 60', between outer bushings 39a,b is a sun gear 50'. Sun gear 50'has teeth to mesh with the teeth of planet gears 40' in a drivingrelation as in known. Coaxially surrounding, and operatively coupledwith, planet gears 40' is a ring gear 80' having internal teeth as isknown.

As shown in the schematic diagrams of 7a and 7b, mechanism 10' willoperate with the handwheel and motor connected in the above-describedpositions. These two components would be reversed if conditions requiredgiving reduction preference to the motor or the handwheel. If thepreference is to have the motor drive the valve primarily, the motorgear 35' acts as a planetary arm and the manual worm gear 28' is lockedby means known in the industry and as explained above. The locking fixesring gear 80' and rotation of the motor worm gear 35' causes the planetgears 40' to drive sun gear 50', and hence drive sleeve 60' and stem59'. When it is desired to move the valve by hand, the motor worm gearis fixed and rotation of the handwheel worm gear 28' transmits torquethrough the idled planet gears 40' to the sun gear 50', and hence todrive sleeve 60' and stem 59'.

What we claim is:
 1. A valve actuator for controlling valve movement,comprising:(a) a bi-directional motor-operated drive means; (b) abi-directional manually-operated drive means; (c) a first worm fixedlyattached to said motor-operated drive means; (d) a second worm fixedlyattached to said manually-operated drive means. (e) a first worm gearoperatively engaged with said first worm; (f) a second worm gearoperatively engaged with said second worm; (g) planetary drive meansoperably connected to said first and second worm gears and to arotatable sleeve member, said planetary drive means comprising:(1) a sungear concentrically disposed about said sleeve member; (2) a pluralityof planet gears operatively engaged with said sun gear; (3) a ring gearconcentrically disposed about said sun gear and operably engaged to saidplurality of planet gears; (h) an elongate stem disposed within saidsleeve member for non-rotational axially reciprocal movement relativethereto in response to rotation of said sleeve member; (i) wherein uponactuation of said motor-operated drive means, said second worm and saidsecond worm gear remain stationary, and wherein upon actuation of saidmanually-operated drive means, said first worm and said first worm gearremain stationary; (j) wherein said sun, ring and planet gears arecoplanar relative to one another and in adjacent parallel planesrelative to said first worm and gear and to said second worm and gear;(k) wherein said first worm and gear have a helix angle is less than thecoefficient of friction between said first worm and said first wormgear; (l) wherein said second worm and gear have a helix angle such thatthe tangent of said helix angle is such that the tangent of said helixangle is less than the coefficient of friction between said second wormand said second worm gear; and (m) wherein said first and second wormgears are each disposed concentrically around said sleeve member.
 2. Thevalve actuator of claim 1 wherein said sun gear is fixedly attached tosaid first worm gear, and wherein said planetary drive means furthercomprises a plurality of carrier arms, each of said carrier arms beingaffixed to said rotatable sleeve member and to one of said planetarygears.
 3. The valve actuator of claim 2, wherein said sun gear isfixedly attached to said first worm gear by a plurality of keys.
 4. Thevalve actuator of claim 2, wherein said sun gear further comprises meansfor supporting said plurality of planet gears.
 5. The valve actuator ofclaim 2, wherein said ring gear is fixedly attached to said second wormgear.
 6. The valve actuator of claim 1, wherein said plurality of planetgears are fixedly attached to said first worm gear, and wherein said sungear is fixedly attached to said sleeve member.
 7. The valve actuator ofclaim 6, wherein said ring gear is fixedly attached to said second wormgear.